The present invention relates in general to heat exchangers and, in particular to a new and useful heat exchanger which is meant to be horizontally disposed in the ground, which can be utilized as a waste heat heat exchanger for power plants or to absorb excess heat from the ground.
The utilization of waste heat from various sources, has become a priority problem. Particularly in power plants, great amounts of energy are produced which are dissipated to the ambience in cooling towers. The use of wet cooling towers for dissipating waste heat is becoming more and more restricted by water economies and the use of dry cooling towers developed recently leads to a reduced utilization of the primary energy in the power plant.
A horizontally extending, buried heat exchanger is known for use as a cooling system for power plants, which utilizes the water-carried waste heat for warming agricultural areas. This makes it possible to increase agriculture yields, extend the period of growth, improve produce quality, and cultivate non-native plants. Further advantages are that the waste heat is employed in a manner which is kind to the enrironment, so that the location of the power plant can be chosen more freely and, as compared to power plants with dry cooling towers, the efficiency is improved.
In the prior art heat exchanger, the geometry of embedding the unit is such that at the forward and return ends of a certain amount of parallel extending cooling pipes, manifolds supplying and discharging the pipes are provided, each comprising a straight pipe which extends perpendicularly to the cooling pipes, in a length corresponding to, or slightly exceeding, the crosswise extension of the associated group of cooling pipes. These manifolds are connected to the forward or return line through a short connecting tube. The individual groups of cooling pipes are laid in the pattern of a grate which is quasi-rigidly fixed on its sides formed by the two straight manifolds, so that the occurring variations in length of the cooling pipes represent a strong mechanical load on the system. This makes the strength over time and the life of the system unsatisfactory and, particularly in power plants, the requirements of economy and safety are not met to a sufficient extent. This is due to the dilations and contractions of the mostly several hundred meters long cooling pipes under temperatures varying between a cold state and an operating level, which are hindered by the straight manifolds which are substantially fixed in their filled up trenches.